interface CompurerAverage{
	public double average(double a,double b);
}
class A implements CompurerAverage{
	public double average(double a,double b){
		double aver=0;
		aver=(a+b)/2;
		return aver;
	}
}
class B implements CompurerAverage{
	public double average(double a,double b){
		double aver=0;
		aver=Math.sqrt(a*b);
		return aver;
	}
}
public class Example6_4{
	public static void main(String[] args) {
		CompurerAverage computer;
		double a=11.23,b=22.78;
		computer=new A();
		double result=computer.average(a,b);
		System.out.printf("%5.2f和%5.2f的算术平均值：%5.2f\n",a,b,result);
		computer=new B();
		result=computer.average(a,b);
		System.out.printf("%5.2f和%5.2f的几何平均值：%5.2f\n",a,b,result);
	}
}
